Good air quality is a fundamental aspect of the quality of life and is an essential component of sustainable development. Poor air quality can contribute to ill health. It also has environmental impacts, such as acidification, eutrophication and damage to vegetation and buildings. During the last 20 years or so the international community has taken action to tackle such problems, particulaly acid rain and urban air polltuion.

To control the spread of transboundary pollution the United Nations Economic Commission for Europe (UNECE) implemented the Convention on Long-Range Transboundary Pollution (1979). Since that time, emissions of sulphur dioxide across Europe have been lowered dramatically, but increases in the volume of traffic have meant that emissions of nitrogen oxides have not fallen as quickly. Consequently, whilst other environmental issues such as global warming and ozone depletion have received more attention in recent years, transboundary acid rain remains a problem today.

In the UK, the Air Quality Strategy identifies clear measurable targets to improve air quality in the UK by 2005, based on understanding of the health effects of the pollutants concerned and costs of emission reduction methods. The Strategy sets out standards and objectives for the 8 main health-threatening air pollutants: carbon monoxide, nitrogen dioxide, sulphur dioxide, particulates, ozone, lead, benzene and 1,3- butadiene. The standards are based on an assessment of the effects of each pollutant on public health. They are based on recommendations by the Expert Panel on Air Quality Standards, standards used by the European Council (EC), and guidelines used by the World Health Organisation. The Strategy sets out the contribution key sectors, such as industry, transport and local government, will need to make towards achieving objectives. Improvements in air quality will not be made without cost. Consequently, the objectives introduced under the Environment Act 1995 will be achieved through the best available techniques not entailing excessive cost.